Oxygenated chemical compounds contain
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
as a part of their chemical structure. The term usually refers to oxygenated chemical compounds added to
fuels. Oxygenates are usually employed as
gasoline additives to reduce
carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
and
soot
Soot ( ) is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolysed ...
that is created during the burning of the fuel. Compounds related to soot, such as
polyaromatic hydrocarbon
A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. ...
s (PAHs) and
nitrated PAHs, are also reduced.
The oxygenates commonly used are either
alcohols or
ether
In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be ...
s:
* Alcohols:
**
Methanol (MeOH)
**
Ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...
(EtOH); see also
Common ethanol fuel mixtures
**
Isopropyl alcohol
Isopropyl alcohol (IUPAC name propan-2-ol and also called isopropanol or 2-propanol) is a colorless, flammable organic compound with a pungent alcoholic odor. As an isopropyl group linked to a hydroxyl group ( chemical formula ) it is the s ...
(IPA)
**
''n''-Butanol (BuOH)
** Gasoline grade
''tert''-butanol (GTBA)
* Ethers:
**
Methyl ''tert''-butyl ether (MTBE)
**
''tert''-Amyl methyl ether (TAME)
**
''tert''-Hexyl methyl ether (THEME)
**
Ethyl ''tert''-butyl ether (ETBE)
**
''tert''-Amyl ethyl ether (TAEE)
**
Diisopropyl ether
Diisopropyl ether is secondary ether that is used as a solvent. It is a colorless liquid that is slightly soluble in water, but miscible with organic solvents. It is used as an extractant and an oxygenate gasoline additive. It is obtained indust ...
(DIPE)
In the United States
In the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
, the
Environmental Protection Agency had authority to mandate that minimum proportions of oxygenates be added to automotive gasoline on regional and seasonal basis from 1992 until 2006 in an attempt to reduce air pollution, in particular
ground-level ozone
Ground-level ozone (O3), also known as surface-level ozone and tropospheric ozone, is a trace gas in the troposphere (the lowest level of the atmosphere of Earth, Earth's atmosphere), with an average concentration of 20–30 parts per billion by v ...
and
smog. In addition to this North American automakers have in 2006 and 2007 promoted a blend of 85% ethanol and 15% gasoline, marketed as
E85
E85 is an abbreviation typically referring to an ethanol fuel blend of 85% ethanol fuel and 15% gasoline or other hydrocarbon by volume.
In the United States, the exact ratio of fuel ethanol to hydrocarbon may vary according to ASTM 5798 that ...
, and their flex-fuel vehicles, ''e.g.''
GM's Live Green, Go Yellow campaign. US
Corporate Average Fuel Economy (CAFE) standards give an artificial 54%
fuel efficiency bonus to vehicles capable of running on 85% alcohol blends over vehicles not adapted to run on 85% alcohol blends.
There is also alcohols' intrinsically cleaner combustion, however due to its lower
energy density it is not capable of producing as much energy per gallon as gasoline. Much gasoline sold in the United States is blended with up to 10% of an oxygenating agent. This is known as oxygenated fuel and often (but not entirely correctly, as there are reformulated gasolines without oxygenate) as reformulated gasoline. Methyl ''tert''-butyl ether (MTBE) was the most common fuel additive in the United States, prior to government mandated use of
ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...
.
References
External links
EPA Definition of Oxygenates
{{Use dmy dates, date=November 2020
Petroleum products
Fuels